Malaria is endemic in over 90 countries world-wide with over 200 million cases and ~ 1million deaths recorded yearly. Of these most of the deaths occur in children and pregnant woman in Sub-Saharan Africa. While a number of effective drug therapies have been developed, drug resistance has compromised the effectiveness of most, and thus it is necessary for the world community to continue to identify and develop new anti-malarial agents if we are to maintain any hope of controlling the disease. This need has fueled the formation of not for profit public private partnerships such as Medicines for Malaria Venture (MMV) to manage the development of new antimalarials. MMV has the largest drug development pipeline for anti malarials world-wide and is involved in projects spanning from early discovery work to clinical trials. In an NIH/MMV funded project we performed a high throughput screen for inhibitors of the essential pyrimidine biosynthetic enzyme dihydroorotate dehydrogenase (DHODH). We identified a triazolopyrimidine class of compounds that were potent and selective inhibitors of the Plasmodium enzyme, and which also had potent activity against the parasite. We subsequently initiated a lead optimization program to improve both potency and in vivo drug-like properties, leading to the identification of a compound that was advanced by MMV as a preclinical candidate in July 2011. This is the first DHODH inhibitor to be advanced as a candidate and it represents the only compound in MMV's portfolio that operates through this mechanism. The compound is currently undergoing GLP toxicology studies as a prelude to starting first in man Phase I trials in Jan 2013, if all goes well. However despite the success of our program only 10-20% of compounds that begin Phase I trials will make it to clinical registration, and thus the risk to a preclinical candidate is even higher. This reality necessitates that we continue efforts to identify a back-up candidate should the current candidate fail to make it to registration. The goals of this proposal are to 1) identify 1-2 additional preclinical candidates targeting PfDHODH. As starting points for our lead optimization program we will use novel chemical scaffolds identified by our HTS program of by that of our collaborators at GSK, and 2) to provide biological support for the current candidate, including drug resistance and drug synergy studies. Our team is experienced, has worked together successfully throughout the development of the triazolopyrimidines, and has the expertise to carry out the full range of lead optimization activities, including medicinal chemistry, X- ray structure determination, enzyme and cell-based assays, and pharmacokinetics and metabolism. MMV will provide funds to support pharmacology and toxicology, in addition to project management, oversight and advisors to further facilitate the project. Successful completion of these aims will identify additional DHODH inhibitors with the potential to be advanced for the treatment of malaria.